design of shafts….

A hoisting drum 0.5 m in diameter is keyed to a shaft which is supported in two

bearings and driven through a 12 : 1 reduction ratio by an electric motor. Determine the power of the

driving motor, if the maximum load of 8 kN is hoisted at a speed of 50 m/min and the efficiency of the

drive is 80%. Also determine the torque on the drum shaft and the speed of the motor in r.p.m.

Determine also the diameter of the shaft made of machinery steel, the working stresses of which are

115 MPa in tension and 50 MPa in shear. The drive gear whose diameter is 450 mm is mounted at the

end of the shaft such that it overhangs the nearest bearing by 150 mm. The combined shock and

fatigue factors for bending and torsion may be taken as 2 and 1.5 respectively.

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